During manufacturing processes involving a substrate, the substrate is transported through the manufacturing process on a transport surface, such as a screen or belt. Many manufacturing processes are conducted at a high speed and the transportation of the substrate at a high speed can result in defects due to movement of the substrate on the transport surface or movement of the transport surface itself.
For example, the substrate, while generally moving in the machine direction of manufacture, can experience side-to-side movement, also known as cross-machine direction weave. This cross-machine direction weave can result in substrates which can be processed incorrectly as the cross-machine direction registration of the substrate will be incorrect. Such process implications can include, for example, cutting lines can be in the wrong locations or graphics can be printed in an offset manner or can be blurred. In addition to the potential of the substrate experiencing cross-machine direction weave, the substrate can also experience “bounce” in the z-direction, in other words, up-and-down movement. If the manufacturing process includes contacting the substrate with a coating, such as, for example, an ink, surfactant, adhesive, or any other transferable medium, and the substrate “bounces,” the substrate could come into direct contact with the source of the transferable medium which can result in fouling of the source as well as an undesirable volume of medium transferring to the substrate. The bouncing of the substrate can also result in inaccurate machine direction placement of the transferable medium onto the substrate because the distance between the source of the transferable medium and the substrate changes. Additionally, a manufacturing process, by its very nature, usually involves multiple types of equipment which can operate at speeds which can differ from one machine to the next. The differentials in speed can result in fluctuations in the tension of the substrate. Fluctuation in tension during a manufacturing process can also be caused by any acceleration and/or deceleration of the manufacturing machinery, any fluctuation in the tension during the unwinding of the substrate as it enters the manufacturing process, as well as by the substrate itself if the substrate has a generally non-uniform shape in either the cross-machine direction or the machine direction (e.g., the substrate may have an egg shape or oval shape rather than a more square or rectangular shape). If the manufacturing process includes contacting the substrate with a coating such as described above, such fluctuations in the tension of the substrate can result in stretching or bunching of the substrate which can result in the transferable medium being incorrectly applied to the substrate.
There is a need to control the movement of a substrate while transporting the substrate through a manufacturing process. There is a need to minimize the cross-machine direction weave of a substrate while transporting the substrate through a manufacturing process. There is a need to minimize the z-direction bounce of a substrate while transporting the substrate through a manufacturing process. There is a need to control the movement of a substrate while transporting the substrate through a manufacturing process so that a transferable medium can be applied to the substrate with greater accuracy.